JPH058126B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing a silica-alumina composite useful as a raw material for a sintered body. (Prior Art and Problems) In recent years, silica-alumina ceramics such as mullite have been attracting attention as substrates for electronic materials because of their low coefficient of thermal expansion and low dielectric constant. In addition, the raw material powder used for ceramic sintered bodies such as the above electronic material substrates is required to have good filling properties, good sinterability, and high purity. Further, from the viewpoint of filling properties and sintering properties, it is desirable that the particle size of the powder is about 0.1 to 1 μm, that is, in the submicron range. There are two possible methods for obtaining such submicron powder. One is the so-called breakdown method, in which large particles are pulverized, and the other is the so-called build-up method, in which particles are precipitated from a solution, for example. However, in general, according to the breakdown method, in order to achieve a small particle size in the submicron range, impurities are inevitably mixed in, making it impossible to obtain highly pure powder. Therefore, synthesis of a powder that satisfies the above requirements is generally carried out by the build-up method. Regarding the synthesis of silica-alumina composites in the submicron range by the build-up method, (1) precipitation method from solution, (2) hydrothermal synthesis method, and (3) spray pyrolysis method are known. Each has the following problems. First, regarding the precipitation method from a solution shown in (1), for example, in JP-A-58-156524, a mixed solution of a hydrolyzable organosilicon compound and a hydrolyzable aluminum organic compound is prepared in an alkaline solvent. A method for synthesizing a composite consisting of silica and alumina by hydrolysis is disclosed. However, according to this method, it is difficult to synthesize a silica-alumina composite containing a large amount of alumina. The hydrothermal synthesis method (2) is reported by Watanabe et al. in the Journal of the Ceramic Industry Association, Vol. 91, No. 6, but this method requires a long reaction time of two days or more, It is hard to say that this is an advantageous method. The spray pyrolysis method (3) was reported by Imai et al. in Report of the Research Laboratories of Engineering Materials (11) 1986. However, according to this method, the presence of sodium is essential to obtain a silica-alumina composite, so it is necessary to remove sodium by ion exchange after synthesis to obtain a pure silica-alumina composite. Therefore, the manufacturing process becomes complicated. (Means for Solving the Problems) In order to solve the above-mentioned problems, the inventors of the present invention have conducted intensive research on a method for producing a silica-alumina composite having a particle size in the submicron range. discovered the method described below and completed the present invention. That is, in the present invention, a mixed solution of a partial hydrolyzate of an organosilicon compound and a hydrolyzable organoaluminum compound in an amount of 0.3 to 3 times the mole of the organosilicon compound is prepared in water or a water-containing solvent having a pH of 5 to 9. This is a method for producing a silica-alumina composite powder, which is characterized in that it is added to and hydrolyzed. The organosilicon compound used in the present invention is not particularly limited as long as it is hydrolyzable, and any known compound can be used. Generally, alkoxysilanes of the formula Si(OR) ₄ are preferably used. R in the formula is an alkyl group, and generally a lower alkyl group having 1 to 5 carbon atoms such as a methyl group, ethyl group, propyl group, butyl group is preferable. In the present invention, it is an important requirement to partially hydrolyze the organosilicon compound in advance, but the partially hydrolyzed product is not particularly limited, and any material that can be further hydrolyzed may be used. Generally, the partial hydrolyzate is composed of a monomer of an organosilicon compound, a dimer, a trimer, or an oligomer of the condensed monomer. The partial hydrolyzate most preferably used in the present invention has a content ratio of the dimer to the endomer.
It ranges from 0.1 to 10, preferably from 0.2 to 6, more preferably from 0.25 to 4. The above content ratio is a representative value representing the degree of partial hydrolysis. Generally, when the degree of partial hydrolysis is low, a large amount of the monomer is present in the partial hydrolyzate without polymerization, and only a small amount of the dimer is produced, so The content ratio of dimers is small. Further, as partial hydrolysis progresses, the monomer polymerizes and decreases, whereas the dimer increases up to a certain point and becomes approximately constant thereafter. Therefore, as the partial hydrolysis progresses, the content ratio of the dimer to the monomer increases. The above content ratio may be measured by any means, but generally by gas chromatography,
It can be measured as the ratio of the peak area of the dimer to the peak area of the monomer. At this time, generally, several peaks representing the monomer appear at a short retention time, for example 2 to 4 minutes, and the dimer appears at a long retention time, for example 4 to 9 minutes. Several peaks appear. The reason why the monomer and dimer peaks are separated into several peaks is not clear, but for example, when alkoxysilane is used as the organosilicon compound, the following hydrolyzate is produced. This is probably because it is being generated.

【formula】

【formula】

[Formula] Furthermore, the reason why the peak of the dimer is separated into several peaks is thought to be due to the generation of hydrolysates as shown below, for example.

【formula】

【formula】

【formula】

[Formula] For the synthesis of the partial hydrolyzate in the present invention, known methods can be employed without particular limitation. A generally preferred method is to add an organosilicon compound and water to a solvent that dissolves both the organosilicon compound and water, and to perform hydrolysis. Examples of solvents that are preferably used include alcohols, ethers, ketones, and the like, with alcohols being particularly preferred.
Among these alcohols, lower alcohols such as methanol, ethanol, propanol, and butanol are preferred, and methanol is most preferably used. The amount of water used in the synthesis of the partial hydrolyzate varies depending on the conditions of partial hydrolysis, and is determined as necessary. Generally, the ratio of the dimer to the monomer contained in the partial hydrolyzate is
In order to make it 0.1 to 10, the amount of water should be 0.2 to 5 times the mole of the organosilicon compound, preferably
It may be in the range of 0.5 to 3 times the mole. Further, an acid or an alkali can be used as a catalyst for the hydrolysis, but an acid catalyst is more preferably used. As the acid catalyst, known ones can be used without particular restrictions, but among them, hydrochloric acid, nitric acid, sulfuric acid,
Mineral acids such as phosphoric acid, organic acids such as formic acid, acetic acid, and malonic acid, and acid type ion exchange resins are suitable. The organoaluminum compound used in the present invention is
Any known hydrolyzable material can be used without particular limitation as long as it is hydrolyzable. Generally suitable organoaluminum compounds include aluminum alkoxide compounds represented by the formula Al(OR') ₃ (where R' is an alkyl group) or alkoxyl groups (OR') of the above formula.
Part or all of is a carboxyl group or β-
There are compounds substituted with dicarbonyl groups. Among the organoaluminum compounds mentioned above, those particularly preferably used include aluminum ethoxide,
aluminum propoxide, aluminum butoxide, aluminum monobutoxypropoxide,
Examples include aluminum ethyl acetoacetate diisopropoxide, aluminum tris (ethylacetoacetate), aluminum monoacetylacetonate bis (ethylacetoacetate), aluminum tris (acetylacetonate), and the like.
Among these, organic aluminum compounds having a dicarbonyl group such as aluminum ethyl acetoacetate diisopropoxide are most preferably used. Further, the amount of the organoaluminum compound is preferably 0.3 to 3 times the mole of the organosilicon compound, more preferably 0.5 to 2 times the mole, and most preferably 0.5 to 1.5 times the mole. preferable. If the amount of the organoaluminum compound is outside the above range, a well-dispersed silica-alumina composite powder cannot be obtained. In the present invention, prior to hydrolyzing the partial hydrolyzate of an organosilicon compound and the hydrolyzable organoaluminum compound, it is necessary to mix them in advance. Without performing the above mixing in advance,
If they are added separately to water or a water-containing solvent, particles in which silicon and aluminum are uniformly composite cannot be obtained. The method for preparing the mixed solution of the partial hydrolyzate of the organosilicon compound and the organoaluminum compound of the present invention is not particularly limited. Generally, while stirring the organoaluminum compound or its solution, the partial hydrolyzate of the organosilicon compound or its solution may be added thereto, and vice versa. Furthermore, if necessary, a partial hydrolyzate of an organosilicon compound and an organoaluminum compound can be added to the soluble solvent during stirring. In the present invention, the solution used to hydrolyze the above mixed solution needs to be water or a water-containing solvent having a pH of 5 to 9, preferably 5 to 7. If the pH of the solution is outside the above range, a well-dispersed silica-alumina composite fraction cannot be obtained, and the product may become gel-like. As a component of the above-mentioned water-containing solvent of the present invention, water and an organic solvent compatible with water can be used without any restriction. Among the organic solvents, alcohols such as methanol, ethanol, propanol, butanol, ethylene glycol, diethylene glycol, and glycerin, ethers such as tetrahydrofuran and dioxane,
Examples include ketones such as acetone and acetylacetone, or mixtures of the above-mentioned organic solvents. Among them, the use of alcohols improves the dispersibility of the obtained powder. Furthermore, the amount of water in the water-containing solvent of the present invention is not particularly limited as long as it can hydrolyze a mixed solution of a partial hydrolyzate of an organosilicon compound and an organoaluminum compound. It is preferably at least 25% by weight, and more preferably at least 25% by weight. In the present invention, the method of hydrolyzing a mixed solution of a partial hydrolyzate of an organosilicon compound and an organoaluminum compound by adding it to water or a neutral water-containing solvent is not particularly limited. In order to rapidly and uniformly hydrolyze the mixture in a neutral water-containing solvent, it is preferable to drop the mixed solution into water or a neutral water-containing solvent that is being stirred. (Effects) By the above method, it is possible to obtain a high-purity silica-alumina composite with very little contamination by other metal oxides, etc., without requiring removal of impurities such as ion exchange after production. Furthermore, the silica-alumina composite can be shaped into a shape having a particle size of 0.1 μm to 1 μm. Furthermore, the silica-alumina composite can be synthesized by varying the alumina content within a wide range. Furthermore, it is sufficient to use a simple stirring tank in the production equipment of the present invention, and no particularly complicated equipment is required. (Examples) Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples. In addition, the content ratio of the dimer to the monomer of the organosilicon compound in the partial hydrolyzate in the following examples was measured as follows. In other words, a gas chromatograph measurement device equipped with an FID detector is used as a gas chromatograph measurement device.
Using GC-9A (manufactured by Shimadzu Corporation), helium was flowed as a carrier gas at a rate of 40 ml/min.
A glass column with a length of 3 m was used, filled with silicon GE and SE-30 (manufactured by Wako Pure Chemical Industries, Ltd.), and the injection temperature was 200°C and the column temperature was 130°C.
°C to 180 °C (temperature raised at a rate of 5 °C/min after sample injection)
Measurements were made with Chromatopack E-13A (manufactured by Shimadzu Corporation) was used for peak detection. Example 1 Tetraethyl silicate (manufactured by Nippon Colcoat)
Dissolve 104g in 250ml of methanol (manufactured by Wako Pure Chemical Industries, Ltd.), add 9g of 0.1N hydrochloric acid, and heat at 20°C.
The mixture was stirred for 3 hours. When the solution was analyzed by the gas chromatography described above, the ratio of the dimer to the monomer in the solution was 2.8. The solution was mixed with 206 g of aluminum ethyl acetoacetate diisopropoxide (manufactured by Kawaken Fine Chemical),
It was added to a mixed solution of 250 ml of ethanol and mixed.
The mixed solution was dropped into a water-containing solvent consisting of 0.8 g of water and 0.8 g of methanol to obtain a silica-alumina composite powder. Observation using an electron microscope revealed that the composite powder was composed of spherical particles of 0.2 to 0.7 μm. Incidentally, the pH of the water-containing solvent was 5.7 according to a PH meter. An electron micrograph showing the particle structure of the composite powder is shown in FIG. Example 2 104 g of tetraethyl silicate was mixed with 250 g of methanol.
ml, 18 g of 0.1N nitric acid was added thereto, and the mixture was stirred at 30°C for 1.5 hours. The solution was prepared in Example 1.
When analyzed in the same manner as above, the ratio of the dimer to the monomer in the solution was 3.7. The solution was mixed with 96 g of aluminum ethyl acetoacetate diisopropoxide and isopropanol (manufactured by Tokuyama Soda).
After adding to 200ml of solution, it was mixed. The mixed solution was added dropwise to 1.5 liters of water with stirring to obtain a silica-alumina composite powder. Observation using an electron microscope revealed that the composite powder was composed of spherical particles of 0.1 to 0.7 μm. The pH of the water was 5.4 according to a PH meter. An electron micrograph of the composite powder is shown in FIG. Example 3 104 g of tetraethyl silicate was mixed with 250 g of methanol.
ml, 9 g of 0.1N hydrochloric acid was added thereto, and the mixture was stirred at 30°C for 30 minutes. When the solution was analyzed in the same manner as in Example 1, the ratio of the dimer to the monomer in the solution was 0.5. This solution was added to a solution of 137 g of aluminum ethyl acetoacetate diisopropoxide and 250 ml of acetone and mixed. Add the mixed solution to 1.2 parts water and isopropanol.
0.3 to obtain a silica-alumina composite powder. Observation using an electron microscope revealed that the composite powder was composed of spherical particles of 0.2 to 0.6 μm. In addition, the pH of the water-containing solvent is PH
According to the meter it was 5.5. Example 4 104 g of tetraethyl silicate was mixed with 250 g of methanol.
ml, 15 g of 1N acetic acid was added thereto, and the mixture was stirred at 30°C for 2 hours. When the solution was analyzed in the same manner as in Example 1, the ratio of the dimer to the monomer in the solution was 3.1. This solution was added to a solution of 137 g of aluminum isopropoxide (manufactured by Kawaken Fine Chemicals) and 200 ml of ethylene glycol, and then mixed. Add 0.8 of the mixed solution to water,
dropwise into a water-containing solvent consisting of methanol, 0.8
A silica-alumina composite powder was obtained. Observation using an electron microscope revealed that the composite powder was composed of spherical particles of 0.2 to 0.8 μm. Example 5 76g of tetramethylsilicate was added to 250g of methanol.
ml, 9 g of 0.1N hydrochloric acid was added thereto, and the mixture was stirred at 30°C for 30 minutes. When the solution was analyzed in the same manner as in Example 1, the ratio of the dimer to the monomer was 6.1. The solution was dissolved in aluminum ethyl acetoacetate diisopropoxide 137
g, was added to a solution of 250 ml of ethanol and mixed.
The mixed solution was dropped into a water-containing solvent consisting of 0.8 ml of water and 0.8 ml of methanol to obtain a silica-alumina composite powder. Observation using an electron microscope revealed that the composite powder was composed of spherical particles of 0.1 to 0.5 μm. Comparative example 1 104g of tetraethyl silicate and 250g of methanol
This solution was added to a solution of 206 g of aluminum ethyl acetoacetate diisopropoxide and 250 ml of ethanol, and then mixed. When this mixed solution was dropped into a water-containing solvent consisting of 0.8 g of water and 0.8 g of methanol, a gel-like substance was formed. Comparative Example 2 104g of tetramethylsilicate was mixed with 250g of methanol.
ml, 9 g of 0.1N hydrochloric acid was added thereto, and the mixture was stirred at 30°C for 1 hour. The solution was dissolved in aluminum ethyl acetoacetate diisopropoxide.
After adding 206 g to a solution of 250 ml of ethanol, they were mixed. When this mixed solution was dropped into a water-containing solvent containing 0.8% of a 0.1N aqueous hydrochloric acid solution and 0.8% of methanol, a gel-like substance was formed. The pH of the water-containing solvent was 1 or less according to a PH test paper. Comparative example 3 104g of tetraethyl silicate and 250g of methanol
ml, 9 g of 0.1N hydrochloric acid was added thereto, and the mixture was stirred at 30°C for 1 hour. The solution was dissolved in aluminum ethyl acetoacetate diisopropoxide.
After adding 206 g to a solution of 250 ml of ethanol, they were mixed. The solution was diluted with ammonia water (ammonia content: 25
%, manufactured by Wako Pure Chemical Industries) 38ml, water 0.71, methanol
When it was dropped into a 0.75% water-containing solvent, a gel-like substance was formed. The PH in the water-containing solvent was greater than 11 according to PH test paper. Comparative example 4 104g of tetramethyl silicate and 250g of methanol
ml, 9 g of 0.1N hydrochloric acid was added thereto, and the mixture was stirred at 30°C for 1 hour. The solution was dissolved in aluminum ethyl acetoacetate diisopropoxide.
After adding 206 g to a solution of 250 ml of ethanol, they were mixed. When a water-containing solvent containing 0.8 of water and 0.8 of methanol was added dropwise to the solution, a gel-like substance was formed.

[Brief explanation of the drawing]

FIGS. 1 and 2 of the accompanying drawings are electron micrographs showing the particle structure of the silica-alumina composites obtained in Example 1 and Example 2, respectively.

Claims (1)

[Scope of Claims] 1. A mixed solution of a partial hydrolyzate of a hydrolyzable organosilicon compound and a hydrolyzable organoaluminum compound in an amount of 0.3 to 3 times the mole of the organosilicon compound is prepared at a pH of 5 to 9. 1. A method for producing a silica-alumina composite, which comprises adding it to water or a water-containing solvent and hydrolyzing it. 2 The particle size of the silica-alumina composite is from 0.1
The manufacturing method according to claim 1, which is a spherical body of 1 μm.